This invention relates generally to parking meters and systems and more specifically to electronic parking meters and systems.
Parking meters permit vehicles to be parked on streets for an allowable time determined by the number and denominations of coins which are placed in the parking meter. A clock mechanism in the parking meter runs down the allowable time until it reaches zero, and an overtime parking indication appears.
The coin receiving devices of the parking meters perform various tests to determine whether an acceptable coin has been inserted, and the denomination of the coin. Circuitry which tests for the presence of ferrous material (i.e., slugs) includes Hall-effect sensors, and frequency shift metallic detectors. The denomination is determined by devices which measure the diameter of the coin such as infra-red emitting diodes and photo-diodes, or which measure the weight of the coin using strain gauges, and the like.
Coin receiving mechanisms which use IR detectors, Hall-effect circuitry, magnetic fields and light sensing rays with microprocessors include U.S. Pat. No. 4,483,431 (Pratt); U.S. Pat. No. 4,460,080 (Howard); U.S. Pat. No. 4,429,648 (Meyer) and U.S. Pat. No. 5,119,916 (Carmen et al.).
In recent years, electronic parking meters and systems have been developed which use microprocessors in conjunction with electronic displays, IR transceivers to communicate with auditors, and ultrasonic transceivers to determine the presence of vehicles at the parking meter. U.S. Pat. Nos. 4,823,928 and 4,967,895 (Speas) disclose electronic parking meters which use microprocessors, electronic displays, IR transceivers, solar power and sonar range finders.
The sophisticated devices which use microprocessors, electronic displays and IR and ultrasonic transducers consume too much power to operate by non-rechargeable batteries alone. Thus, the Speas' patents disclose the use of solar power cells which charge capacitors or rechargeable batteries.
Various problems exist with the use of solar power sources including the use of parking meters in shady areas, or the use of parking meters during periods in which there is very little sunlight. This causes the rechargeable batteries to run down, and they require frequent replacement. Or, in the case of the use of capacitors, the lack of power causes the meter to become inoperative.
There is therefore a need for an electronic parking meter, with a microprocessor, electronic display, ultrasonic and IR transceivers, which is specifically designed for low power drainage so that it can operate for extended periods of time with ordinary batteries. The parking meter of this invention utilizes unique low-power coin sensing and detecting devices and circuitry as well as several conditions or states of operation to minimize power requirements in usage. This enables the electronic parking meter to operate strictly on battery power without the use of unreliable solar power sources or the requirement to run and connect power cables to the meters.